The present invention relates generally to the field of art of bone fixation devices, also known as intramedullary devices, which are inserted into the medullary canal of a fractured bone to promote the healing of the fractured bone and to facilitate the functional rehabilitation of the fractured bone.
The present invention also relates to the field of devices which are used to align the broken bone.
The present invention further relates to a system used in the operating room by a surgeon and the assisting medical personnel which allows the fractured bone to be aligned with a reduced risk of exposure to radiation and then fixed.
When a bone is broken, the surgeon aligns the bone manually with the aid of imaging equipment, such as, a fluoroscope and then immobilizes the various bone segments using one or more rigid devices that span the fracture site. These devices are located either externally to the body, internally on the exterior of the bone cortex or internally in the medullary canal of the bone.
The external devices are generally exterior frames which enter the body and attach to the bone by metal pins, such as a Hoffman device or a Brooker frame. The disadvantages of these devices are the difficulties in manipulating the devices to achieve the desired compressive force required to unite the bone segments, the inadvertent manipulation after the devices are set in the desired position and the increased chance of infection along the metal pins penetrating the skin and underlying tissue.
The internal devices which contact the exterior of the bone cortex are cortical plates. These plates are implanted surgically and attached to the bone cortex by screws. Cortical plates can apply compression to the bone segments but have many disadvantages; such as, the danger of damaging vital structures by extensive dissection of muscle and periosteum, the increased possibility of infection and the increased chances of necrosis and non-union of the bone fragments by decreased blood supply to the fragments.
The internal devices which are located in the medullary canal are intramedullary nails or devices which are surgically implanted into the medullary canal. These devices minimize soft tissue dissection and destruction and reduce the chances of infection. However, the earliest types of these devices were too small in diameter to facilitate rehabilitation or too large in diameter resulting in a weakened bone shaft and reduction in the blood supply to the end of the fractured bone as a result of enlarging the medullary cavity. Further, these prior art intramedullary nails provided limited lateral support by only contacting the inner wall of the medullary cavity of the bone over a small region. Additionally none of them provided a compression force along the length of the bone.
Later improved intramedullary devices did increase lateral support of the fractured bone by using an intramedullary device having an expandable end portion. However, these devices sometimes included complex mechanisms to effect the expansion and these devices were relatively expensive. U.S. Pat. Nos. 3,760,802 and 4,453,539 are examples of these devices.
A more recent intramedullary device is disclosed in U.S. Pat. No. 5,057,103, which allegedly provides compressive force along the length of the bone to close the fracture and promote healing. This intramedullary nail has a straight, non-flexible cylindrically shaped outer member and a cylindrically shaped inner member which fits into the outer member. The inner member has hinged arms for engaging the interior of the bone cortex in the distal bone segment and is moved from stowed position to deployed position by sliding the inner member toward the outer member in a distal direction. A U-shaped member for engaging the cortex on the proximal bone segment is also present. The arms of this intramedullary nail are only 0.174 inches wide and 0.078 inches thick. From FIG. 1 of this patent, it can be seen that the arms engage the bone cortex in the metaphysis of the bone. The compression force that is applied to the bone results from adjusting this force across the fracture site with the arms and U-shaped member.
The bone fixation device of the present invention is an intramedullary nail which also provides a compression force to the bone; however, the configuration of the bone fixation device of the present invention is considerably different than that of the device disclosed in U.S. Pat. No. 5,057,103. In addition to providing a compression force to the bone, the present invention provides additional advantages over the device disclosed in U.S. Pat. No. 5,057,103 as well as all of the prior art intramedullary nails.
The present invention also provides a device which aligns the broken bone and holds it in the aligned position while the bone fixation device is being inserted into the medullary canal. This bone alignment manipulation has heretofore been performed using the hands of the surgeon or the hands of the assisting medical personnel while monitoring the progress with a fluoroscope or some other comparable imaging apparatus. Even though the medical personnel use lead aprons and barriers over the trunk of the body as protection against the radiation, the hands and arms of the personnel are exposed to frequent doses of radiation during the same operation. Thus, there is a need to provide a device which can align and hold the aligned broken bone in place while the intramedullary device is being inserted.
The present invention also discloses a system for use in the operating room to fix a broken bone where the broken bone is aligned with the bone alignment device of the present invention and then fixed with the bone fixation device of the present invention. The present invention provides an improved system for fixing broken bones by reducing the risk of overexposure to radiation by medical personnel and by providing an improved intramedullary bone fixation device with several features to apply compressive force to the fractured bone and which allows adjustment and replacement of portions of the device while the remaining portion of the device is still inserted in the intramedullary canal.